(a) Technical Field
The present invention relates to a device and a method for controlling a high side direct current/direct current (DC/DC) converter of a hybrid vehicle. More particularly, the present invention relates to a device and a method for controlling a high side DC/DC converter of a hybrid vehicle, in which the switching frequency of the high side DC/DC converter is variably adjusted based on temperatures of an inductor and an insulated-gate bipolar transistor (IGBT) switching element, which constitute the high side DC/DC converter, thereby maintaining a balance between the temperatures of the inductor and the IGBT switching element.
(b) Background Art
To maximize the efficiency of a drive motor of an eco-friendly vehicle such as a hybrid vehicle or an electric vehicle, a method of driving a motor is changed from a method of driving a motor by directly converting a voltage of a high-voltage battery using an inverter to a method of driving a motor using an inverter by primarily increasing energy of a high-voltage battery using a high side DC/DC converter. Accordingly, a high side DC/DC converter (hereinafter, referred to as a HDC) for primarily increasing a voltage of a high-voltage battery and applying the increased voltage to an inverter is mounted within a plug-in hybrid vehicle, an electric vehicle, etc., of which demand has recently been increased. The HDC is configured with several types of semiconductor elements such as an inductor and an IGBT to increase the operating voltage of a drive motor.
Referring to FIG. 1, the HDC is a boost circuit disposed between a high-voltage battery 10 and an inverter 30 for motor drive control. The HDC includes an inductor 22 connected to an output terminal of the high-voltage battery 10, and an upper IGBT switching element 24 and a lower IGBT switching element 26, which switch current flowing through the inductor 22.
The HDC 20 operates as a boost converter when a driving voltage is supplied to a motor through the inductor 22, and operates as a buck converter for charging the high-voltage battery 10 when regenerative braking is performed. The switching operation of the HDC 20 is performed by applying PWM signals inverted to each other to gates of the respective upper and lower IGBT switching elements 24 and 26.
In particular, switching loss occurs in switching on/off operations of the upper and lower IGBT switching elements. When the motor is driven, switching loss occurs in the lower IGBT switching element. When regenerative braking is performed, the switching loss occurs in the upper IGBT switching element. The switching loss increases as the switching frequency of the HDC increases. Further, the amount of loss occurring in driving of the IGBT switching element of the HDC increases the temperature of the IGBT switching element. As the amount of loss occurring in the IGBT switching element increases, the number of IGBT switching elements to be driven should increase. Furthermore, unit cost increases by the increased number of IGBT switching elements.
Meanwhile, accordingly the related art, a method of decreasing a switching frequency is used as the method reducing the amount of switching loss occurring in the IGBT switching element. When the switching frequency is decreased, the amplitude of ripple current of the inductor increases, which causes the inductor to generate heat.